The first two points should be categorized as ‘static comfort’ according to Champoux et al [1]. In this
study the focus will be on point 3: ‘dynamic comfort’. Vibrations are oscillatory motions, which can
occur in different forms. The magnitude of the vibrations can be measured as a displacement, velocity or
acceleration. Most common is to measure the acceleration, which will also be used in this research.
Analyzing vibrations can be done in multiple domains; in most cases the frequency domain is more useful
than the time domain. The frequency domain reveals harmonic signals which cannot be seen in the time
domain. The root mean square (RMS) value can be used as an indicator of the severity of the vibrations.
This RMS value can be calculated both from the data in the frequency domain and the data in the time
domain. When the vibrations consist of shocks or are non-stationary the root mean quad (RMQ) is more
useful [2].
The Eigen frequencies of most organs and limbs are in the region between 0.5 Hz and 10 Hz [3].
Vibrations with strong frequency components in this region will decrease the comfort of the cyclist.
Frequencies above 10Hz are of less importance.
For measuring vibrations, recently developed MEMS (Micro Electro-Mechanical Systems)
accelerometers represent a promising technology. These MEMS accelerometers are small and cheap, and
many of them feature digital outputs, multiple axes and low power consumption. These properties make
them ideal to measure movement in sports.